Hook fastener



FIG. 1 is a top plan view of a hook fastener depicting my new design, the side opposite being substantially a mirror image;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof; and

FIG. 5 is a right side elevational view thereof. 

The ornamental design for a hook fastener, as shown. 